MEDIUM CVSS 6.5
Published: 2026-06-30

CVE-2026-10655

zephyrproject zephyr Security Advisory (CVE-2026-10655)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-10655 impacting zephyrproject zephyr. Evaluated with CVSS Base Score of 6.5 (MEDIUM).

Original NVD Description

Source: NIST NVD
The asynchronous SNTP client in Zephyr (subsys/net/lib/sntp/sntp.c, sntp_close_async) closed the UDP socket file descriptor directly from the calling thread immediately after detaching it from the network socket service, without synchronizing with the socket-service poll thread. The socket service thread polls each socket via zvfs_poll, which (in zsock_poll_prepare_ctx) registers a k_poll_event pointing into the socket's net_context (&ctx->recv_q) and then blocks in k_poll without holding a reference or lock. net_context objects are allocated from a fixed pool (contexts[CONFIG_NET_MAX_CONTEXTS]) and reused after close. When sntp_close_async is invoked from a different thread than the poll thread (in the in-tree consumer subsys/net/lib/config/init_clock_sntp.c, the SNTP timeout handler runs on the system workqueue while the socket service thread is blocked in poll on the same fd), the close frees and may reuse the net_context while the poll thread still has a poller node linked into the freed object, resulting in a use-after-free / object confusion of kernel poll structures. The SNTP timeout path is the normal no-response failure mode, so a network peer or off-path attacker who drops or delays the SNTP/NTP response can drive the racing close repeatedly (and periodically with NET_CONFIG_SNTP_INIT_RESYNC). The most likely consequence is a crash of the networking thread (denial of service), with potential memory corruption when the freed context slot is reallocated. The fix defers the close to the socket service thread itself via net_socket_service_close (NET_SOCKET_SERVICE_CLOSE_SOCKETS), so the same thread that polls performs the close, eliminating the race. Affected releases: v4.2.0 through v4.4.0.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Network (AV:N)
Exploitable remotely across internet boundaries
Attack Complexity
High (AC:H)
Depends on race conditions or environment
Privileges Required
None (PR:N)
Unauthenticated execution
User Interaction
None (UI:N)
Zero human interaction required
Scope
Unchanged (S:U)
Confined to same security context
Confidentiality
None (C:N)
No data confidentiality impact
Integrity
Low (I:L)
Partial data modification possible
Availability
High (A:H)
Total denial of service or shutdown

🎯 Affected Versions Matrix

Affected Product zephyrproject / zephyr
Affected Versions *
Weakness Enumeration CWE-416

Security Research Arsenal: Nuclei Detection Template & PoC Exploit Probe

High-Intent Research Tool

Ready-to-use security scanner signatures, active verification probe skeletons, and remediation playbooks for CVE-2026-10655 impacting zephyrproject zephyr.

⚡ Nuclei Detection Template (YAML) cve-2026-10655.yaml
id: cve-2026-10655

info:
  name: zephyrproject zephyr - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: medium
  description: |
    Automated signature & scanner for CVE-2026-10655 affecting zephyrproject zephyr.
    Evaluation: The asynchronous SNTP client in Zephyr (subsys/net/lib/sntp/sntp.c, sntp_close_async) closed the UDP socket file descriptor directly from the calling ...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-10655
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
    cvss-score: 6.5
    cve-id: CVE-2026-10655
    cwe-id: CWE-416
  tags: cve,cve-2026-10655,zephyrproject,zephyr,medium

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "zephyr"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-10655.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-10655
# Target: zephyrproject zephyr | CVSS: 6.5 (MEDIUM)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-10655 (zephyrproject zephyr)...")
    headers = {
        "User-Agent": "CyberVault-Audit-Scanner/2.0",
        "Accept": "*/*"
    }
    try:
        r = requests.get(f"{target_url.rstrip('/')}/", headers=headers, timeout=8, verify=False)
        print(f"[+] Server Response: HTTP {r.status_code} | Server Banner: {r.headers.get('Server', 'Unknown')}")
        if r.status_code < 500:
            print(f"[!] Target reachable. Verify version against zephyrproject zephyr scope (*).")
        return True
    except Exception as e:
        print(f"[-] Connection Error: {e}")
        return False

if __name__ == '__main__':
    url = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:8080"
    verify_vulnerability(url)
🛡️ Quick Patch & Remediation Script (Bash) patch_cve-2026-10655.sh
# Recommended Remediation & Patching Commands for CVE-2026-10655
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install zephyr 2>/dev/null || \
sudo dnf upgrade zephyr 2>/dev/null || \
sudo yum update zephyr

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i zephyr 2>/dev/null || rpm -qa | grep -i zephyr

# 3. Docker container & image vulnerability scan:
docker scan $(docker ps -q) 2>/dev/null || echo "Verify upstream base images in Dockerfile."

🛡️ Remediation & Security Action

  • Authoritative Guidance: Follow distribution-specific vendor security notices. Advisory status and package patches vary by distribution release.
  • Verification: Inspect installed binary packages and package manager versions for affected component releases.
  • Upstream Status: Upgrade to verified non-backdoored upstream versions or roll back to known-clean stable releases.
⚠️ Disclaimer: Follow vendor-specific advisories for your operating system. CyberVault does not fabricate unsupported remediation scripts.

🔗 Verified Technical References

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-10655 in zephyrproject zephyr?

Review vendor-specific security notices and update zephyrproject zephyr packages to the latest patched release immediately. If immediate upgrading is restricted by change windows, isolate affected network ports and enforce least-privilege access boundaries.

Is there an active exploit or public PoC for CVE-2026-10655?

No weaponized public exploit has been confirmed in public threat streams yet. Continuous surveillance is active across GitHub and security feeds.

What is the CVSS 3.1 severity rating and impact for CVE-2026-10655?

CVE-2026-10655 is classified with a CVSS 3.1 Base Score of 6.5 (MEDIUM). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
6.5
MEDIUM SEVERITY
CVE ID CVE-2026-10655
Weakness CWE-416
Vendor zephyrproject
Product zephyr
Published 2026-06-30
Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H